The invention pertains to pallets carrying component devices for example such as a transmission housing, engine block, pump housing, transaxle housing or other device to which components are to be added and assembled, and the loaded pallets moved into and through testing stations. The conveyor system moving such pallets with the supported devices include roller conveyors, positive drive conveyors, or other similar translation means conventionally used in mechanical manufacturing facilities. The pallets of the prior art have been made of solid metal such as steel. To these are fixedly mounted, for securement of the component device being assembled and tested, a plurality of fixtures spaced apart from each other at intervals upon the top upper surface of the pallet. These fixtures removably engage and secure the component device to the pallet.
The steel pallets conventionally use plastic or resilient composition bumper bars on their side edges so that as the pallets move on the conveyors the shock and impact of contact with next preceding and following pallets are somewhat cushioned. Nevertheless, the steel pallet is substantially inflexible, being about 11/2 inches in thickness, approximately 26 inches wide by about 34 inches long. These steel pallets weigh about 300-350 pounds each, and with the usual fixtures for mounting and securing an average-size transmission housing and assembly elements, the total unit can weigh well over 500 pounds. A man working at the production line conveyor system on which these pallets move, cannot lift such a pallet except by the aid of a mechanical hoist or lift truck. Therefore, removal of damaged units, be they pallets or the component devices carried thereon, significantly interferes time-wise with an orderly production line. The steel units do have one important advantage, namely that the dimensional change of the pallet is insignificant during its translation on the production line. Since the various stations for assembly and testing are predetermined, the length, width and thickness of the pallet and the related positioning of the component device therein being considered, dimensional changes in the pallet of any significant measure cannot be tolerated.
The principal disadvantages of the steel pallets are their excessive weight and difficulty in handling, even by mechanical means, as well as the time delays on a high-speed production line if and when the loaded pallet requires removal therefrom.
Another significant disadvantage, particularly at the present time, is the need for large quantities of energy in power and equipment to move such loaded heavy steel pallets from station to station in the line. Since the steel pallet performs primarily only a load bearing function, the reduction of weight in the pallet, while maintaining its dimensional stability, is a most desirable goal.